This invention is directed to ultraviolet light (UV) curable coating compositions containing chlorinated polyolefins. The compositions are particularly useful as coatings for a variety of plastic substrates (both thermoplastic and thermoset), especially as basecoats for providing a glass-like smooth surface to the plastic to which a thin film of metal can be subsequently deposited via, for example, vacuum deposition or sputtering.
It is known to apply a thin film of metal to a nonmetallic substrate to make a metallized substrate and to provide the metallized substrate with a protective coating. Such coated, metallized substrates are useful, for example, for such diverse articles as nonmetallic parts on automotive vehicles, and containers and container caps for cosmetics. The plastic substrates for such articles often are composed of heat sensitive materials such as heat sensitive plastics which can distort when exposed to elevated temperatures. The plastic substrate itself typically contains many surface irregularities which prevents attainment of a good mirror finish if the thin layer of metal is deposited directly thereon.
Accordingly, a basecoat of an organic coating composition generally is first used to coat the plastic substrate, and the thin layer of metal is subsequently deposited over the basecoat. However, often adequate adhesion between the plastic substrate and the basecoat can not be achieved. One proposed method of solving this adhesion problem with respect to polyolefin substrates, as described in U.S. Pat. No. 4,303,697, is to treat the surface of the polyolefin substrate with a solution of a chlorinated polyolefin material in a solvent, allow the solvent to evaporate optionally at an elevated temperature, and then expose the resulting dry surface to ultraviolat radiation. In this art known method, the treated surface of the polyolefin substrate is then subsequently painted with the coating composition to be adhered. However, this process has the disadvantages of requiring the steps of applying the solvent solution of chlorinated polyolefin to the polyolefin substrate, allowing the solvent to evaporate, and then exposing the dry surface to ultraviolet radiation before the paint to be adhered is even applied.
It would be desirable to be able to apply organic coating compositions directly to a variety of plastic substrates without having to carry out steps such as those described in U.S. Patent No. 4,303,697 (summarized above) for treating polyolefin substrates, and still achieve excellent adhesion of the organic coatings directly to the plastic substrates under a variety of conditions. Moreover, it would be desirable to provide coatings for a variety of plastic substrates which can be cured efficiently, which provide excellent adhesion to the underlying plastic substrate, and which can provide a glass smooth surface for subsequent metallization. These and other objects will become apparent to one skilled in the art from the disclosure contained herein.